The Spectrapure refurbished 90gpd unit is one of the best deals around. You basically get a new unit for around $125 and get Spectrapure quality. Who knows what you will get from ebay. You may get a junkie RO membrane that only runs at 90%. You should be looking at 98% or better with 95% being the bottom for efficiency. The lower the efficiency the quicker you will go thru the DI resin, which means it will be more expensive in the long run because you are having to buy new DI resin more often. You also have no idea of the quality of the prefilters on the ebay unit. The prefilters protect the RO membrane so you want them to be high quality since the RO membrane is the most expensive component. Of course their are extras you can add that you don't really need to get the price up to the $200+ range. Personally I don't think you will go wrong with a unit from Spectrapure, BRS, Buckeyes or Melevs. I have a 20+ year old Kent Marine unit and it just recently blew an 0-ring. I just bought a new canister from BRS since I didn't know where to get a replacement 0-ring for it. It isn't the normal round shape, it is flat on one side. Plus I figured it would be nice to have a clear canister instead of the blue one.